1. Why are earthquakes monitored worldwide instead of in earthquake-prone areas only? 2. How many seismographs are needed to find the epicenter of an earthquake? Why is this
number significant?

earthquakes are monitored worldwide because we never know when they will occur, they can happen everywhere in the world even in the areas that are far away from the tectontic plates boundaries. that is why earthquakes are monitored worldwide instead of in earthquake-prone areas only.

the "dirty dozen" chemicals banned in an international treaty are formally known as persistent organic pollutants, or pops. the united nations environment program provided this background on what they are and what they can do to humans and wildlife.

i hope this